Comparative in vitro evaluation of microgap in titanium stock versus cobalt-chrome custom abutments on a conical connection implant: Effect of crown cementation and ceramic veneering.

OBJECTIVE: To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation. MATERIAL AND METHODS: Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05). RESULTS: Mean values (µm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups. CONCLUSIONS: Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap.

Current applications of 3D printing in dental implantology: A scoping review mapping the evidence.

OBJECTIVES: This scoping review aimed to identify the available evidence in the use of 3D printing technology in dental implantology. Due to the broad scope of the subject and its application in implantology, three main areas of focus were identified: (1) customized dental implants, (2) manufacturing workflow for surgical implant guides, and (3) related implant-supported prostheses factors, which include the metallic primary frameworks, secondary ceramic or polymer superstructures, and 3D implant analog models. MATERIALS AND METHODS: Online databases (Medline, Cochrane, Embase, and CINAHL) were used to identify the studies published up to February 2023 in English. Two experienced reviewers performed independently the screening and selection among the 1737 studies identified. The articles evaluated the additive manufacturing (AM) technology, materials, printing, and post-processing parameters regarding dental implantology. RESULTS: The 132 full-text studies that met the inclusion criteria were examined. Thirteen studies of customized dental implants, 22 studies about the workflow for surgical implant guides, and 30 studies of related implant-supported prostheses factors were included. CONCLUSIONS: (1) The clinical evidence about AM titanium and zirconia implants is scarce. Early data on survival rates, osseointegration, and mechanical properties are being reported. (2) 3D printing is a proven manufacturing technology to produce surgical implant guides. Adherence to the manufacturer's instructions is crucial and the best accuracy was achieved using MultiJet printer. (3) The quality of 3D printed prosthetic structures and superstructures is improving remarkably, especially on metallic alloys. However, better marginal fit and mechanical properties can be achieved with milling technology for metals and ceramics.

Accuracy of five different 3D printing workflows for dental models comparing industrial and dental desktop printers.

OBJECTIVES: The aim of this study was to evaluate the accuracy, in terms of trueness and precision, of printed models using five different industrial and dental desktop 3D printers. MATERIALS AND METHODS: Full-arch digital models with scanbodies of 15 patients were printed with five different 3D printers. The industrial printers were 3D system Project MJP2500 (3DS) and Objet30 OrthoDesk (Obj). The dental desktop printers were NextDent 5100 (ND), Formlabs Form 2 (FL) and Rapidshape D30 (RS). A total of 225 printed models were analysed. The printed models were digitized and compared with the reference cast model using the Control X software (Geomagic). The descriptive statistics and one-way ANOVA with the post hoc Tukey test were performed (α = 0.05). RESULTS: The one-way ANOVA for the trueness and precision of the printed model presented the best results for the 3DS, followed by ND, Obj, FL and RS (P < 0.01). In the scanbody zone, the best results were for the 3DS group, followed by Obj, ND, FL and RS (P < 0.01). Comparing the technologies, the Multijet technology used in industrial printers presented better results than the DLP and SLA technologies used in dental desktop printers (P > 0.01). CONCLUSIONS: There were statistically significant differences in terms of the accuracy of the printed models, with better results for the industrial than the dental desktop 3D printers. CLINICAL RELEVANCE: The industrial 3D printers used in dental laboratories presented better accuracy than the in-office dental desktop 3D printers, and this should be considered when the best accuracy is needed to perform final prosthetic restorations.

The effect of a convergent transmucosal neck on soft tissues and radiographic outcomes: a 1-year follow-up randomized controlled trial.

PURPOSE: The aim of this randomized controlled clinical trial was to evaluate peri-implant marginal bone levels (MBLs) and soft tissue dimension changes 1 year after loading. Patients in the control group received bone-level implants, whereas in the test group, tissue-level implants with a convergent transmucosal neck were used. MATERIAL AND METHODS: MBLs were calculated by measuring the distance from the implant shoulder to the first visible bone-to-implant contact using standardized periapical digital radiographs. Baseline (day of loading) and follow-up digital models obtained with an intraoral scanner were used to quantify the changes in the peri-implant soft tissue dimensions with a best-fit algorithm. RESULTS: The difference between final and baseline MBLs showed a mean bone loss of 0.16 ± 0.01 mm in the test group (n = 15) and 0.45 ± 0.09 mm in the control group (n = 14) (p > 0.05). Soft tissue contour at the level of the gingival margin (GM) increased by 1.96 ± 2.69 mm in the test group and 0.65 ± 0.42 mm in the control group (p = 0.167). Both groups showed a coronal displacement of the gingival margin with no significant differences among them. CONCLUSIONS: The present study demonstrated peri-implant hard and soft tissues stability at both implant designs with no significant differences 12 months after loading. CLINICAL RELEVANCE: There is still insufficient scientific evidence to demonstrate the role and advantages of the convergent transmucosal neck on the behavior of the peri-implant soft and hard tissues stability compared to a straight neck in bone-level implants 12 months after loading.

Influence of age, training, intraoral scanner, and software version on the scan accuracy of inexperienced operators.

PURPOSE: To evaluate the effect of operator age on the scan accuracy (trueness and precision) of inexperienced operators when compared with experienced operators, and how training, intraoral scanner (IOS), and software version affect scan accuracy. MATERIAL AND METHODS: Thirty-four operators were sorted into groups: G1 (operators <25 years old, no experience), G2 (operators >40 years old, no experience), and G3 (experienced IOS operators). They conducted partial-arch scans before and after a 4-session training with two IOSs (Trios 3 and True Definition) and two software versions. These scans were compared with the reference scans obtained from conventional impressions and a laboratory scanner (IScan D103i) to evaluate trueness (mean root mean square values) and precision (standard deviation of root mean square values) with a software program (Geomagic Control X). Kruskal-Wallis and post-hoc Dunn's tests were used to evaluate the effect of age on the scan accuracy of inexperienced groups when compared with experienced operators, while the effect of training, IOS, and software version on scan accuracy was evaluated with Wilcoxon or Mann-Whitney U tests (α = 0.05). RESULTS: Before training, G1 and G2 scans had similar accuracy (p ≥ 0.065). After training, G1 scans had higher accuracy when IOS data was pooled and had higher precision with TD (p ≤ 0.004). Training increased the scan accuracy (p < 0.001), while newer software increased the trueness of inexperienced operator scans (p = 0.015). CONCLUSIONS: Age affected the scan accuracy of inexperienced operators after training, indicating that extended training may be required for older operators. Training increased the scan accuracy, and newer software increased the trueness of inexperienced operator scans.

Efficacy and risks of tooth-supported prostheses in the treatment of partially edentulous patients with stage IV periodontitis. A systematic review and meta-analysis.

AIM: The aim was to evaluate the efficacy and effectiveness of tooth-supported fixed prostheses in partially edentulous patients with stage IV periodontitis. MATERIAL AND METHODS: Randomized and controlled clinical trials (RCTs and CCTs) and prospective/retrospective cohort studies or case series were searched in three databases. Survival rate of abutment teeth was considered the primary outcome. Meta-analyses were performed whenever possible. RESULTS: Twenty-four publications were included. No RCTs or CCTs compared the efficacy of tooth-supported fixed prostheses between patients with severe periodontitis or non-periodontitis patients. Most of the data retrieved were derived from case series. The incidence of abutment-tooth loss after a follow-up period from 2 to 35.4 years was low (n = 17 studies; weighted mean incidence (WMI) = 4.8%; confidence interval (CI) [3.2, 6.5]). The corresponding figure for prostheses failure was WMI = 6.9% (n = 18; 95% CI [4.1, 9.7]). Technical complications seemed to be more frequent than biological complications (caries, endodontic failure, root fracture, etc.). Periodontal outcomes tended to remain stable over time. CONCLUSION: Tooth-supported fixed prostheses seemed to be a valid treatment approach to restore masticatory function in patients with stage IV periodontitis once periodontal therapy has been accomplished. However, the comparative efficacy of this treatment among periodontitis and non-periodontitis patients is unclear due to the absence of clinical trials.

Diagnosis of Interproximal Caries Lesions in Bitewing Radiographs Using a Deep Convolutional Neural Network-Based Software.

The aim of this study was to evaluate the diagnostic reliability of a web-based artificial intelligence program for the detection of interproximal caries in bitewing radiographs. Three hundred bitewing radiographs of patients were subjected to the evaluation of a convolutional neural network. First, the images were visually evaluated by a previously trained and calibrated operator with radiodiagnosis experience. Then, ground truth was established and was clinically validated. For enamel caries, clinical assessment included a combination of clinical-visual and radiography evaluations. For dentin caries, clinical validation was performed by instrumentally accessing the cavity. Second, the images were uploaded and analyzed by the web-based software. Four different models were established to analyze its evaluations according to the confidence threshold (0-100%) offered by the program: model 1 (values >0% were considered positive and values of 0% were considered negative), model 2 (values ≥25% were considered positive and values <25% were considered negative), model 3 (values ≥50% were considered positive and values <50% were considered negative), and model 4 (values ≥75% were considered positive and values <75% were considered negative). The accuracy rate (A), sensitivity (S), specificity (E), positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and areas under receiver operating characteristic curves (AUC) were calculated for the four models of agreement with the software. Models showed the following results respectively: A = 70.8%, 82%, 85.6%, 86.1%; S = 87%, 69.8%, 57%, 41.6%; E = 66.3%, 85.4%, 93.7%, 98.5%; PPV = 42%, 57.2%, 71.6%, 88.6%; NPV = 94.8%, 91%, 88.6%, 85.8%; PLR = 2.58, 4.78, 9.05, 27.73; NLR = 0.2, 0.35, 0.46, 0.59; AUC = 0.767, 0.777, 0.753, 0.701. Findings in the present study suggest that the artificial intelligence web-based software provides a good diagnostic reliability on the detection of dental caries. Our study highlighted model 2 for showing the best results to differentiate between healthy teeth and decayed teeth.

Clinical study comparing the accuracy of interocclusal records, digitally obtained by three different devices.

OBJECTIVE: The aim of the present cross-sectional study was to compare the interocclusal contact records obtained by three different digital methods (intra- and extraoral digital scanners and T-Scan III system) with the conventional method (articulating paper). MATERIALS AND METHODS: Twenty-five healthy volunteers were selected. As a control group, maximum intercuspation occlusal contacts were registered and photographed from the patients with an 8 µm articulating paper. Then, intraoral conventional elastomer impressions were taken and after obtaining the corresponding plaster models of every patient they were scanned with an extraoral scanner (Zfx Evolution, Zimmer Biomet Dental) (group 1). Moreover, digital impressions were made with an intraoral scanner (Trios Color POD, Phibo, 3Shape) and contacts were also registered (group 2). Finally, T-Scan III records were made and stored for further analysis (group 3). Two previously calibrated examiners independently evaluated the interocclusal contacts from every group. Data was analyzed by using Kappa index test and Pearson's chi-square test. Diagnostic tests and ROC curve were also performed. RESULTS: Kappa interoperator index was 70.6% (better agreement). In Kappa intraoperator index, the best value was obtained in the intraoral scanner group (moderate agreement) and the worst with T-Scan III group (low agreement). ROC curve showed highest values in the intraoral scanner group (0.817) and lowest values in the T-Scan III group (0.613). CONCLUSION: Results suggest greater reliability to record occlusal contacts with the intraoral scanner. CLINICAL RELEVANCE: Intraoral scanners seem to be reliable in registering intermaxillary occlusal contacts when compared with the current gold standard.

Clinical outcomes of the biologically oriented preparation technique (BOPT) in fixed dental prostheses: A systematic review.

STATEMENT OF PROBLEM: The biologically oriented preparation technique is a concept with a vertical tooth preparation, gingitage, an immediate interim restoration preserving the clot, and a specific laboratory technique aiming to adapt the marginal periodontal tissue to a remodeled emergence profile of the crown. However, the published scientific evidence on this subject is limited. PURPOSE: The purpose of this systematic review was to analyze whether using the biologically oriented preparation technique leads to improved clinical outcomes in terms of probing depth, gingival inflammation index, gingival marginal stability, and fewer mechanical and biological complications. MATERIAL AND METHODS: Recommendations from the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used in this systematic review. An electronic search of the MEDLINE/PubMed, EMBASE, Science Direct, Wiley Online Library, Cochrane, and ProQuest databases was made for articles published between March 2010 and July 2021 using keywords. Three reviewers selected and analyzed all articles that mentioned the biologically oriented preparation technique and met the inclusion criteria. RESULTS: A total of 6 articles met the inclusion criteria: 1 prospective randomized clinical study, 1 randomized clinical study, 1 prospective clinical study, and 3 case series. According to these studies, of all the teeth treated with the biologically oriented preparation technique, probing depth (greater than 3 mm) increased in only 2.3%, gingival inflammation was present in 22.8%, gingival recession occurred in 1.7% (decreased gingival stability), and mechanical and biological failures occurred in 4.4% of the teeth. CONCLUSIONS: Fixed dental prosthesis treatments performed following the concept of the biologically oriented preparation technique did not increase probing depth and showed a moderate rate of gingival inflammation, lower recession rates, and lower mechanical and biological failures at the 5-year follow-up. The biologically oriented preparation technique appears to be a viable alternative technique for obtaining satisfactory and stable clinical results up to 5 years. Long-term randomized clinical trials are recommended to reach more conclusions about this protocol.

Accuracy of digitization obtained from scannable and nonscannable elastomeric impression materials.

STATEMENT OF PROBLEM: Elastomeric impression materials have been marketed for optimizing direct digital acquisition without requiring a stone cast. The trueness and precision of the digitization of these new elastomeric impression materials are unclear. PURPOSE: The purpose of this in vitro study was to compare the trueness and precision of digital dental casts obtained from the direct digitization of 2 types of vinylsiloxanether (VSXE) impression materials by using a laboratory laser scanner. MATERIAL AND METHODS: Thirty-eight elastomeric impressions were made of a master die with a similar morphology to a premolar crown preparation. The impression materials were Identium (IDE) and Identium Scan (SCAN), designed for direct digitalization. Each impression was digitalized by using an optical scanner to create digital casts. A computer-aided design (CAD) reference model of trueness (CRM) was created and aligned to each digital cast for digital 3-dimensional discrepancy analysis. RESULTS: The mean ±standard deviation global trueness of IDE was 53 ±16 µm and that of SCAN was 46 ±3 µm. SCAN digital casts showed higher precision (58 ±5 µm) than IDE (69 ±18 µm) (P<.05). At the margin of the preparation and at the axial surfaces, SCAN models showed higher trueness (3 ±6 µm and 1 ±5 µm) than IDE (15 ±10 µm and 2 ±37 µm), respectively. CONCLUSIONS: Scannable impressions could be digitalized with higher global precision than conventional elastomeric materials. Higher trueness could be achieved in specific impression locations such as gingival areas or axial walls of preparations, where the light emitted by the scanner was not blocked.

Original versus nonoriginal cast-to-gold abutment-implant connection: Analysis of the internal fit and long-term fatigue performance.

STATEMENT OF PROBLEM: Restoring implants with nonoriginal abutments is common. However, studies that evaluated compatible abutments with long-term fatigue performance are lacking. PURPOSE: The purpose of this in vitro study was to assess the internal fit and the cyclic fatigue life after artificial aging of 3 implant-abutment configurations restored with 1 original and 2 compatible nonoriginal cast-to-gold abutments. MATERIAL AND METHODS: Forty-eight original internal hexagon connection implants were connected to 3 different brands of abutments (n=16): 1 original to the implant system and the other 2 with nonoriginal abutments. Internal fit and the percentage of surface with tight contact were assessed by scanning electron microscopy in 12 cross-sectioned specimens (n=4) at 3 different areas (platform, internal, and screw). Thirty-six implant-abutment-crown specimens (n=12) were immersed in artificial saliva and thermocycled for 10 000 cycles between 5 °C and 55 °C. Subsequently, a cyclic load test, as per International Organization for Standardization (ISO) Standard 14 801, was completed in a universal testing machine at 2 Hz in air. RESULTS: The original abutments presented the best fit and highest percentage of tight contact in the internal areas. In addition, the original abutments showed the lower cyclic fatigue strength degradation and the highest long-term success. CONCLUSIONS: Occlusal loads are transferred more homogenously through the system when original abutments are used because of the better fit between the internal components, leading to increased fatigue resistance.

Fatigue fracture resistance of titanium and chairside CAD-CAM zirconia implant abutments supporting zirconia crowns: An in vitro comparative and finite element analysis study.

STATEMENT OF PROBLEM: Zirconia abutments with a titanium base are promising candidates to substitute for titanium abutments based on clinical studies reporting good short-term survival rates. However, information on the long-term performance of zirconia abutments supporting ceramic crowns is scarce. PURPOSE: This in vitro comparative and finite element analysis study compared the fatigue life performance of ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic restorations and zirconia abutments fabricated with a chairside workflow connected to a titanium interface versus titanium abutments. MATERIAL AND METHODS: Twenty-two internal connection implants were divided into 2 groups, one with a zirconia abutment and monolithic ceramic zirconia crown (ZZ) and the other with a titanium abutment and zirconia crown (TiZ). They were subjected to a fatigue test to determine the fatigue limit and fatigue performance of each group as per International Organization for Standardization (ISO) 14801. Microstructural analysis of the fracture surfaces was conducted by using a scanning electron microscope (SEM). Simulations of the in vitro study were also conducted by means of finite element analysis (FEA) to assess the stress distribution over the different parts of the restoration. RESULTS: The fatigue limit was 250 N for the TiZ group and 325 N for the ZZ group. In both groups, the screw was the part most susceptible to fatigue and was where the failure initiated. In the zirconia abutment models, the stress on the screw was reduced. CONCLUSIONS: Chairside CAD-CAM zirconia abutments with a titanium base supporting zirconia crowns had higher fatigue fracture resistance compared with that of titanium abutments.

Fibroblast Interaction with Different Abutment Surfaces: In Vitro Study.

BACKGROUND: Attaining an effective mucosal attachment to the transmucosal part of the implant could protect the peri-implant bone. AIM: To evaluate if chair side surface treatments (plasma of Argon and ultraviolet light) may affect fibroblast adhesion on different titanium surfaces designed for soft tissue healing. METHODS: Grade 5 titanium discs with four different surface topographies were subdivided into 3 groups: argon-plasma; ultraviolet light, and no treatment. Cell morphology and adhesion tests were performed at 20 min, 24 h, and 72 h. RESULTS: Qualitative observation of the surfaces performed at the SEM was in accordance with the anticipated features. Roughness values ranged from smooth (MAC Sa = 0.2) to very rough (XA Sa = 21). At 20 min, all the untreated surfaces presented hemispherical cells with reduced filopodia, while the cells on treated samples were more spread with broad lamellipodia. However, these differences in spreading behavior disappeared at 24 h and 72 h. Argon-plasma, but not UV, significantly increased the number of fibroblasts independently of the surface type but only at 20 min. Statistically, there was no surface in combination with a treatment that favored a greater cellular adhesion. CONCLUSIONS: Data showed potential biological benefits of treating implant abutment surfaces with the plasma of argon in relation to early-stage cell adhesion.

Comparative study of all-ceramic crowns obtained from conventional and digital impressions: clinical findings.

OBJECTIVE: To compare clinical aspects of all-ceramic crowns fabricated from conventional and digital impressions. METHODS: Thirty patients with 30 posterior teeth with the need of a crown restoration were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (TRIOS®, 3shape) and two-step silicone impression technique. Two external blinded operators evaluated the all-ceramic crowns. Five selection items were assessed of which four were clinical: "marginal fit," "occlusal contacts," "interproximal contact points," and "primary retention." Then, the last selection item "final selection" was assessed when the operators considering all the variables had to select which of the digital or conventional crown had the best clinical conditions. Data was analyzed using Kappa index test and the Pearson's chi-square test (α = 0.05). RESULTS: For the items marginal fit and interproximal contact points, moderate agreement between the two operators was described and significant differences were found between the two study groups. Conversely, for the variables primary retention and occlusal contacts, the agreement between the operators was fair and no significant differences were found. For the final selection, a substantial agreement was reached between the two operators and significant differences were found between the two groups (p < 0.05). CONCLUSION: In most cases and in a significant way, the digital crowns had better clinical conditions according to both evaluators. The digital crowns were statistically superior for the interproximal contact points and marginal fit. For the variables occlusal contacts and primary retention, no difference between the two groups was observed. CLINICAL SIGNIFICANCE: Digital intraoral impressions can be used for manufacturing ceramic crowns, with the same or better clinical results as conventional impressions.

Mechanical fatigue behaviour of different lengths screw-retained restorations connected to two designs prosthetic connection level.

The aim of this work is to compare the mechanical fatigue behaviour of different crown heights of single crown implant restorations made over two different internal hexagonal titanium dental implant connection levels. Two different groups of internal hexagonal connection were studied: (a) TL group (N = 26) included implants with a transmucosal connection (12.2 mm height and 4.8 mm width) and (b) BL group (N = 26) composed by implants at a bone level connection (10 mm height and 3.8 mm width). Two subgroups (N = 13) were established for each connection level according to crown heights (TL10 = 10 mm, TL15 = 15 mm, BL12 = 12 mm, BL17 = 17 mm). Dynamic load tests were carried out according to ISO Norm 14801. Failed samples and fracture surfaces were analysed with an optical and scanning electron microscope (SEM). The fatigue limit and the fatigue strength degradation (fatigue strength exponent) decreases with increasing crown height (5 mm) in both groups of internal hexagonal titanium dental implant connection levels. Consequently, the mechanical integrity of internal hexagonal dental implants varies with the height of the crown. An increase of 5 millimetres in the crown height appears to significantly decrease the fatigue life of both types of dental implants.

Obtaining reliable intraoral digital scans for an implant-supported complete-arch prosthesis: A dental technique.

This article describes a technique for obtaining an accurate complete-arch digital scan for an edentulous patient. To achieve this, an auxiliary polymeric device that simulates a denture is designed, fabricated, and placed in the mouth. This device, having the geometry of a typical dental arch, facilitates the digitalization of the edentulous complete arch. This is because the change in radius of the curvature (change of geometry) enables the scanner to perform a more accurate alignment. Initially, the necessary location of the implants is acquired, and then the soft tissue is added. This technique can achieve accurate complete-arch digital scans. Distances between implants are closer to the gold standard when using this auxiliary geometry piece than those obtained without using it.

Analysis of Surface Roughness, Fracture Toughness, and Weibull Characteristics of Different Framework-Veneer Dental Ceramic Assemblies after Grinding, Polishing, and Glazing.

PURPOSE: To compare the surface roughness and biaxial flexural strength of dental ceramics obtained after chairside surface modification by mechanical polishing procedures, versus laboratory reglazing. MATERIALS AND METHODS: Discs (16 × 1.5 ± 1.6 mm) (N = 90) of various framework-veneering combinations were fabricated: D/FC: lithium disilicate/feldspathic ceramic; Z/AL: zirconium dioxide/aluminous ceramic; N/FC: noble alloy/feldspathic ceramic; N/FF: noble alloy feldspathic with fluorapatite; B/FC: base alloy/feldspathic ceramic; B/FF: base alloy/feldspathic ceramic with fluorapatite. In each group 10 specimens were ground using a diamond bur (46 µm) and five were polished with silicone-reinforced disc polishers (25 µm). Surface roughness (Ra) was measured using contact profilometry. After thermocycling in artificial saliva (6000 cycles, 5 to 55 ± 5°C), biaxial flexural strength was measured using "piston-on-three ball" test. The data (N) were analyzed using one-way ANOVA, Bonferroni, and Tukey's posthoc tests. Weibull distribution values were calculated. RESULTS: Surface roughness was significantly higher in the ground group only (p < 0.0001). Mean fracture toughness was significantly lower for chipping (RK: 287, HS: 22, ISO: 1099 MPa) than for total fracture (p < 0.05), (RK: 841, HS:64, ISO: 3222 MPa). For chipping, Weibull distribution presented the highest shape value (m) for D/FC (3.82-5.07) and for total fracture for B/FC (3.69-4.6). CONCLUSION: Chairside surface polishing restored veneer ceramic roughness and mechanical strength to the level of glazing. Feldspathic ceramic with fluorapatite presented better polishing results than conventional feldspathic ceramic did. Ceramic fused to metal was more resistant than lithium disilicate or zirconium dioxide framework-veneer assemblies. Lithium disilicate framework veneered with feldspathic ceramic presented more durability against chipping. CLINICAL IMPLICATIONS: After chairside occlusal modifications in the surfaces of cemented all-ceramic or fused-to-metal FDPs, mechanical polishing procedures should always be carried out.

Original vs. non-original abutments for screw-retained single implant crowns: An in vitro evaluation of internal fit, mechanical behaviour and screw loosening.

OBJECTIVES: To assess the internal accuracy, mechanical behaviour under static load and screw loosening before and after cyclic loading of implant-supported crowns restored with original components or with two compatible non-original brands. MATERIALS AND METHODS: Sixty-three dental implants were divided into three groups (n = 21 each): Group 1 used original components, and groups 2 and 3 used non-original components. Internal accuracy was measured throughout a cross section of the sample groups (n = 8) using scanning electron microscopy (SEM) to evaluate the fit for implant-abutments, implant-crowns and crown-abutments. To evaluate load-bearing capacity, eight samples from each group were loaded until fracture according to ISO Norm 14801. The removal torque value (RTV) was evaluated in the screws connecting the crown with the abutment and the abutment with the implant before and after cyclic loading (2 x 106 cycles) in five samples from each group. The data were analysed using the Kruskal-Wallis test (p < 0.05). RESULTS: Statistically significant differences were found among the mean crown-abutment gaps measured in Group 1 (9.3 µm), Group 2 (45.4 µm) and Group 3 (44.9 µm). Higher values for mean load-bearing capacity were found in Group 1 (1,098 N) than in groups 2 and 3 (1,057 and 973 N, respectively); however, these differences were not statistically significant. Original abutment-implant screws exhibited lower percentages of torque reduction than the non-originals. CONCLUSIONS: Enhanced fit is expected when original components are used. The original abutments exhibited lower percentages of torque reduction after cyclic loading than non-originals.

Intraoral versus extraoral digital occlusal records: a pilot study.

The aim of the present pilot study was to analyze the reliability of interocclusal contact records generated with an intraoral scanner (TRIOS Standard) and an extraoral scanner (Zfx Evolution). Ten patients were selected. The number of occlusal contacts was first determined with the conventional method using 8-µm articulating paper (gold standard) (control). These conventional records were then compared with the intra- and extraoral digital records. Diagnostics tests (sensitivity, specificity, predictive values for positives and negatives), receiver operating characteristic (ROC) curve, and Cohen's kappa coefficient were performed to analyze the data. The kappa index of the extraoral scanner (40.7%) was considered to be 'moderate,' and better than that of the intraoral scanner (26.1%), which was considered to be 'low.' The extraoral scanner showed better results in the diagnostic test and in the ROC curve. The first results suggest that the extraoral scanner is more reliable for recording occlusal contacts than the intraoral scanner.